The present invention relates to a microwave oven, and more particularly, to an interconnection between inner and outer casings of the oven.
A microwave oven is cooking equipment wherein microwaves generated by a magnetron are radiated into a cooking chamber for inductively heating food in the cooking chamber.
FIG. 8 is an exploded perspective view of a conventional microwave oven. As shown in FIG. 8, the microwave oven includes an outer casing 110 defining an outer appearance of the oven, and an inner casing 120 forming a cavity 130. In the outer casing 110, an upper plate portion 111 and two sidewall portions 112 and 113 are integrally formed in an inverted U-shaped form. The inner casing 120 has a front plate 121, a rear plate 123 and a bottom plate 125 which respectively form a front opening, a rear opening and a bottom opening.
The outer periphery of the front plate 121 includes top and side edges which have bent flanges 122 formed thereon. The inner casing 120 includes a cavity casing 126 which is connected with the front plate 121, the rear plate 123 and the bottom plate 125 to form therewith a cooking chamber 130. A door 133 is connected with the front plate 121, which rotatably opens and closes the front opening, which constitutes an access opening of the cooking chamber 130. The door 133 is mounted by means of hinges 131 which are disposed on the upper and lower ends of the left side of the front plate 121 of the inner casing 120. Further, a control panel 135 having a plurality of manipulation buttons 136 for controlling the microwave oven is connected to the right side of the front plate 121.
A component chamber 140 is formed between the outer casing 110 and the cavity casing 126 of the inner casing 120. A magnetron 141, a high-voltage transformer 142 for inducing high voltage, and a high-voltage capacitor 143 for applying a high voltage are installed in the component chamber 140. A cooling fan 144 for blowing air toward the magnetron 141 is installed on the rear plate 123 of the component chamber 140.
Screw connection holes (not shown) are formed along the upper, left and right edges of the rear plate 123. The front edges of the upper plate portion 111 and both sidewall portions 112 and 113 are bent to form a Z-shaped stopper portion 115 in the form of an internal strip. A rear edge of each of the plate portions 111, 112, 113 is defined by a bent portion 118 which is bent perpendicularly relative to the respective plate portion. Screw connection holes 119 are formed in the bent portions 118.
During assembly of the inner and outer casings, the stopper portions 115 of the outer casing 110 receive respective flange portions 122 of the front plate 121, as shown in FIG. 8A. At the same time, the bent portions 118 formed along the rear edge of the outer casing 110 will engage the edge of the rear plate 123 of the inner casing 120, and are tightly fixed thereto by screws inserted into the screw connection holes 119.
It is difficult to achieve and retain a precise orientation between the front plate 121 and the outer casing. Due to limits in the amount of accuracy that can be achieved in the process of bending-over the front edge of the upper plate portion 111 when forming the stopper portions 115, a distance from the front 111A of the upper plate portion 111 to a rear wall 111B of the stopper portion 115 is non-uniform along the length of the stopper portion. Hence, it is possible for the front plate 121 to become skewed relative to the outer casing during the assembly work, whereby gaps or clearance between the front plate and outer casing can easily occur. This complicates the assembly process and makes it difficult to locate various parts in a precise relationship to one another.
Also, during a transportation or operation of the microwave oven, the front plate is susceptible to being displaced relative to the outer casing by external forces to thereby degrade the appearance thereof as well as damage the internal electrical components and disconnect lead wires.